| No. of Crania. | Sex. | Capacity | Capacity | Capacity |
| Average. | Maximum. | Minimum. | ||
| 45 | Male | 1365 | 1625 | 1144 |
| 35 | Female | 1219 | 1528 | 1040 |
Santa Barbara Islands and Mainland.
| No. of Crania. | Sex. | Capacity | Capacity | Capacity |
| Average. | Maximum. | Minimum. | ||
| 9 | Male | 1324 | 1441 | 1167 |
| 5 | Female | 1247 | 1316 | 1175 |
Among exceptional features claimed as more or less a racial characteristic of American crania, the os Incæ, or epactal bone in the occiput, has been noted as present in various stages of manifestation in 3.81 per cent; and among ancient Peruvian crania in 6.08 per cent; while it does not apparently exceed 2.65 per cent in the Negro; and only reaches 1.19 per cent in Europeans.[[181]] In so far as this may be regarded as a sign of arrested development, it is noteworthy as thus occurring in excess in the small-headed, yet highly ingenious and civilised Peruvian race. Dr. Morton noted as a remarkable fact that the skull of the Peruvian child appeared to equal in size that of other races; so that in a much ampler sense than in the perpetuation of a suture of the occiput beyond the stage of fœtal development, the small-sized skull and brain of the adult Peruvian is abnormal. But he followed out his observation of the phenomena no farther than to state, in summing up his investigations “On the internal capacity of the cranium in the different races of men:”[[182]] “Respecting the American race, I have nothing to add, excepting the striking fact that of all the American nations, the Peruvians had the smallest heads, while those of the Mexicans were something larger, and those of the barbarous tribes the largest of all,” namely:—
| { Peruvians, collectively | 75 | cubic | inches. | |
| Toltecan Nations | { | |||
| { Mexicans, „ | 79 | „ | „ | |
| Barbarous Tribes | 82 | „ | „ |
The enlarged tables given in the catalogue of Dr J. Aitken Meigs, increase this inverse ratio of cerebral capacity, thus:—
| Peruvians | 75.3 |
| Mexicans | 81.7 |
| Barbarous Tribes | 84.0 |
“The great American group,” he says, “is, in several respects, well represented in the collection. It includes 490 crania and 13 casts, making a total of 503 from nearly 70 different nations and tribes. Of this large number 256 belong to the Toltecan race (embracing the semi-civilised communities of Mexico, Bogota, and Peru), and 247 to the barbarous tribes scattered over the continent. Of 164 measurements of crania of the barbarous tribes, the largest is 104 cubic inches; the smallest 69; and the mean of all 84. One hundred and fifty-two Peruvian skulls give 101 cubic inches for the largest internal capacity, 58 for the smallest, and 75.3 for the average of all.”[[183]]
The results which Professor Jeffreys Wyman arrived at from a careful comparative measurement of the Squier collection, were confirmed by his subsequent study of that of Professor Agassiz, and may be quoted as applying to both; for he sums up his later investigations with the remark: “These results agree with all previous conclusions with regard to the diminutive size of the ancient Peruvian brain.”[[184]] Of the Squier collection he says: “The average capacity of the fifty-six crania measured agrees very closely with that indicated by Morton and Meigs, namely, 1230 centimetres, or 75 cubic inches, which is considerably less than that of the barbarous tribes of America, and almost exactly that of the Australians and Hottentots as given by Morton and Meigs, and smaller than that derived from a larger number of measurements by Davis. Thus we have, in this particular, a race which has established a complex civil and religious polity, and made great progress in the useful and fine arts,—as its pottery, textile fabrics, wrought metals, highways and aqueducts, colossal architectural structures and court of almost imperial splendour prove,—on the same level, as regards the quantity of brain, with a race whose social and religious conditions are among the most degraded exhibited by the human race. All this goes to show, and cannot be too much insisted upon, that the relative capacity of the skull is to be considered merely as an anatomical and not as a physiological characteristic; and unless the quality of the brain can be represented at the same time as the quantity, brain measurement cannot be assumed as an indication of the intellectual position of races any more than of individuals.”[[185]]
The only definite attempt of Dr. Morton to solve the difficulty thus presented to us, curiously evades its true point. “Something,” he says, “may be attributed to a primitive difference of stock; but more, perhaps, to the contrasted activity of the two races.” Here, however, it is not a case of intellectual activity accompanied by, and seemingly begetting an increased volume of brain; but only the assumption of greater activity in the small-brained race to account for its triumph over larger-brained barbarous tribes in the attainment of numerous elements of a native-born civilisation. The question is, how to account for this intellectual activity, with all its marvellous results, attained by a race with an average brain of no greater volume than that of the Bushman, the Australian, or other lowest types of humanity.